Oil-based ballpoint pen with smooth ink. Ultra fine type 0.02 inch (0.5 mm). [Features] Smooth ink oil-based ballpoint pen / acro ball 0.02 inch (0.5 mm) version. Uses newly developed oil-based ink that allows for smooth and deep writing. The grip part is made of a proprietary soft and non-slip rubber material that prevents slippage and provides a firm grip. Retractable. [How to use] Press the knob and knock the refill.